Elastic laminates (e.g., multilayered materials having elastic properties) are used in a wide variety of absorbent articles. An elastic laminate generally has the ability to be stretched, and once the stretching force is removed, the material can retract and recover. In many applications, it is also desirable that the elastic laminates are soft and not sticky or tacky, as such laminates are often in contact with a user's skin. Moreover, in some instances, such elastic laminates are intended to be used more than one time. For example, the elastic laminates used for diaper ears that contain fastening mechanisms to secure the waistband of a diaper around a wearer may be unfastened and refastened multiple times to adjust the fit of the diaper or to check for insults in the diaper. Meanwhile, other elastic laminates can be included in an absorbent article in predetermined locations to optimize fit, make the article more comfortable to wear through improved fit, and/or improve the ability of the article to absorb liquids while preventing leakage through improved containment structures and gasketing.
Regardless of the particular absorbent article end use, elastic laminates can be made using various methods. In one method, a nonelastic component is joined to an elastic component while the elastic component is in a stretched condition so that when the elastic component is relaxed, the nonelastic component gathers between the locations where it is bonded to the elastic component. The resulting elastic laminate material is stretchable to the extent that the nonelastic component gathered between the bond locations allows the elastic component to elongate. It has been found that stretch bonded laminate materials tend to be fairly costly to manufacture and their inclusion in a product necessarily increases the cost of the end product to the consumer. It would therefore be desirable to provide efficient method for forming elastic materials having the desired level of softness and at a lower cost.
It is also known to laminate (or bond) a necked (neckable) material to an elastic sheet to produce a neck bonded laminate as described in U.S. Pat. No. 5,226,992 to Morman, et al. This process involves an elastic member being bonded to a non-elastic member while only the non-elastic member is extended in one direction (usually the machine direction) and necked in the transverse direction (usually the cross-machine direction) so as to reduce its dimension in the direction orthogonal to the extension. However, the production of such laminates is often not efficient, and the desired elastic properties may not be achieved, such as 200% elongation in the cross-machine direction, because elongation in the cross-machine direction is limited due to necking.
Another method of forming elastic laminates involves extrusion casting an elastic film onto a nonwoven facing or casting a film and adhesively bonding the film to at least one nonwoven facing. Then, the laminates can be subsequently incrementally stretched, such as by grooving, to provide machine direction or cross-machine direction stretch materials depending on the direction of the grooving. For example, machine direction grooving of the laminates allows cross-machine direction stretch by decoupling the facings from the elastic and cross-machine grooving of the laminates allows for machine direction stretch. However, in order to groove an elastic material to decouple the nonwoven facing from the elastic, the facing has often been based on a bonded carded web because the short length of the bonded carded web fibers and the decreased bonding area allows for the nonwoven facing to be grooved or striated while the elastic film remains continuous and undamaged. However, forming bonded carded webs and then grooving such webs is an expensive and time consuming, inefficient process requiring multiple steps. Further, the use of short fibers in the bonded carded web increases the amount of fiber pull out, which is not always desirable depending on the end-use application. On the other hand, it has been observed that the use of other nonwoven facings besides bonded carded webs, such as spunbond facings based on polypropylene with longer fibers and a larger percentage bond area cannot be grooved easily to provide elastic laminates that stretch and recover because of the materials used and the amount of post bonding, which also limits the softness of such materials compared to, for instance, polyethylene-based facings, which are also more cost effective. Further, grooving tends to loosen the fibers in such facings, which leads to difficulty in hook engagement and potentially increased fiber pull out, which can create challenges when utilizing these facings in absorbent article fastening systems. Also, the use of meltblown facings, although they may be easily grooved, is not ideal because of the loosely configured or fuzzy appearance and lack of integrity of the meltblown facings, as well as the potential disadvantages associated with fiber pull out in absorbent article applications.
As such, a need exists for a laminate utilizing meltblown or spunbond facings with sufficient elasticity, groovability, comfort, and softness that can also be used in absorbent article applications where minimal fiber pullout and durability are desired.